In manufacturing electronic devices such as semiconductor devices or liquid crystal display device, a processing such as, for example, film forming or etching is performed on a workpiece to be processed (“workpiece”). In the processing of such a workpiece, a plasma processing apparatus is widely used. As a kind of such a plasma processing apparatus, a parallel plate type plasma processing apparatus is used.
The parallel plate type plasma processing apparatus is provided with a processing container, a mounting table, and a shower head. The mounting table includes a lower electrode and is provided in the processing container. The shower head is provided above the mounting table so as to supply a processing gas to the inside of the processing container toward a workpiece mounted on the mounting table. In addition, the shower head constitutes an upper electrode. In such a parallel plate type plasma processing apparatus, the processing gas is supplied from the shower head to the inside of the processing container, and a high frequency electric field is generated between the upper electrode and the lower electrode. As a result, plasma of the processing gas is generated and the workpiece is processed by the molecules in the processing gas and/or active species of the molecules.
In the plasma processing apparatus, it is required to reduce variation of processing over the entire in-plane region of the workpiece. Japanese Patent Laid-Open Publication No. 2009-117477 discloses a plasma processing apparatus which allows a flow rate of a processing gas supplied to a plurality of in-plane regions of the workpiece and/or gas species to be adjusted in order to reduce the variation of processing.
Specifically, the plasma processing apparatus of Japanese Patent Laid-Open Publication No. 2009-117477 includes a plurality of gas diffusion chambers which are provided coaxially in the shower head. That is, a first gas diffusion chamber is provided at a central region of the shower head, an annular second gas diffusion chamber is provided outside the first gas diffusion chamber, and an annular third gas diffusion chamber is provided outside the second gas diffusion chamber. In addition, the plasma processing apparatus of the Japanese Patent Laid-Open Publication No. 2009-117477 includes a plurality of gas branch paths and is configured such that processing gases from gas sources are respectively supplied to the plurality of gas diffusion chambers through the gas branch paths at a controlled flow rate.